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It's a sign of just how many questions remain unanswered in the investigation into Stephen Paddock's motive: The FBI plans to erect billboards in Las Vegas asking people to call in tips about the gunman and his shooting spree, reports the AP. "If you know something, say something," said agent Aaron Rouse. "We will not stop until we have the truth." Other developments:

Prostitute? Authorities think Paddock hired a prostitute in the days before the shooting, reports ABC News. Investigators were interviewing local call girls hoping to track her down.

Cruises: Paddock wasn't just a regular at casinos—he also took at least 20 cruises, reports CNN. It's not clear which cruise line he sailed, but the ships stopped in Spain, Italy, Greece, Jordan, and the United Arab Emirates, among other places. Girlfriend Marilou Danley accompanied Paddock on at least nine of the cruises. The best guess is that Paddock took the trips to spend time in the ships' casinos.

Only shooter: Police laid to rest any speculation that another gunman helped in the attack. "He was the only shooter; I'm very confident of that," says Las Vegas Metropolitan Police Department Undersheriff Kevin McMahill, per NBC News. "I'm also confident that there were no other people in the room leading up to this event." Authorities were initially puzzled by a phone charger that didn't seem to belong to Paddock, but they now say it matches one of his phones.

Father's church: The Las Vegas Review-Journal has more information on Paddock's bank-robber dad, reporting that Benjamin Paddock sought to open a church in Vegas when he was in his 60s. Paddock called himself a self-ordained minister and actually incorporated Holy Life Congregation, but it never quite took off. “He wanted (to locate the church) in Nevada because he liked to go there and gamble,” says a woman who was friends with him at the time.

Police twins: One of the police officers wounded in the attack was 33-year-old Casey Clarkson, who was at the scene trying to usher people to safety and help the wounded. Meanwhile, his identical twin, Sgt. Branden Clarkson, was back at the station helping coordinate the police response when he learned the news. The New York Times recounts their "harrowing night." (Casey Clarkson is fine and, in fact, returned to duty that night after being treated—and hugging his brother.)